EXCHANGE 


'AT  ' 


New  Results  in  Electro-Analysis 


THESIS 

Presented  to  the  Faculty  of  the  Department  of   Philosophy 
of  the  University  of  Pennsylvania,  in  Partial  Fulfil- 
ment of  the  Requirements  for  the  Degree 
of  Doctor  of  Philosophy 


BY 
THOMAS  POTTER  McCUTCHEON,  JR. 

PHILADELPHIA,  PA. 

1907 


PHILADELPHIA 

THE  JOHN  C.  WINSTON  CO. 

1907 


New  Results  in  Electro-Analysis 


THESIS 

Presented  to  the  Faculty  of  the  Department  of   Philosophy 
of  the  University  of  Pennsylvania,  in  Partial  Fulfil- 
ment of  the  Requirements  for  the  Degree 
of  Doctor  of  Philosophy 


BY 
THOMAS  POTTER  McCUTCHEON,  JR. 

PHILADELPHIA,  PA. 

1907 


PHILADELPHIA 

THE  JOHN  C.  WINSTON  CO. 

1907 


The  writer  takes  this  opportunity  to  express  his  entire 
indebtedness  to  the  suggestions,  advice  and  unfailing  kind- 
ness of  DR.  EDGAR  F.  SMITH  for  any  merit  which  this 
investigation  may  possess. 


INTRODUCTION 

Previous  workers  in  electro-chemical  analysis  have 
directed  their  efforts  almost  entirely  to  the  determination 
and  separation  of  metals.  A  year  ago,  J.  H.  Hildebrand,* 
working  in  this  Laboratory,  showed  that  such  anions  as  Br, 
I,  PO4,  Fe(CN)6,  CNS  could  be  determined  in  the  elec- 
trolytic way.  He  employed  the  mercury  cathode  and  an 
attackable  silver  anode  in  a  cell  especially  devised  for  the 
purpose.  Sodium  and  potassium  can  be  determined  simul- 
taneously, so  that  a  complete  analysis  of  such  salts  as  sodium 
chloride  and  potassium  ferrocyanide  can  now  be  made  with 
ease  and  accuracy. 

The  purpose  of  the  first  part  of  this  investigation  was 
to  extend  this  work  to  the  estimation  of  other  anions  and 
to  learn  whether  other  metals  than  silver  could  be  advan- 
tageously used  as  anodes.  In  the  second  part  of  the  work, 
the  same  form  of  cell  was  used  in  the  separation  of  certain 
metals. 

APPARATUS 

The  decomposition  cell,  devised  by  Edgar  F.  Smith  and 
Hildebrand,  consisted  of  a  crystallizing  dish,  the  bottom  of 
which  was  covered  with  a  layer  of  mercury.  Inside  of  this 
was  placed  a  beaker  of  smaller  diameter,  without  a  bottom 
and  supported  so  that  its  lower  edge  extended  just  below 
the  surface  of  the  mercury.  The  inner  cup  was  held  in 
position  by  means  of  three  corks  placed  radially.  The  mer- 
cury was  connected  with  the  cathode  by  means  of  a  stout 
platinum  wire  enclosed  in  a  glass  tube. 

The  inner  compartment  contained  the  solution  to  be 
analyzed.  Water  was  placed  in  the  outer  compartment,  to 

*Jr.  Amer.  Chem.  Soc.,  XXIX,  4,  447. 

(3) 


444325 


which  a  few  drops  of  sodium  chloride  solution  WQFC  added 
to  increase  the  conductivity  and  a  nickel  wire  to  aid  in  the 
decomposition  of  the  amalgam. 

The  anode  consisted  of  two  disks  of  platinum  gauze, 
placed  one  above  the  other  and  supported  by  a  platinum  rod. 
It  was  plated  with  silver  by  making  it  the  cathode  in  a  bath 
of  silver  potassium  cyanide.  It  was  then  washed,  dried  and 
weighed.  It  was  rotated  250-300  times  per  minute  by 
means  of  a  small  motor.  The  anode  was  lowered  into  the 
inner  compartment  until  the  upper  gauze  was  covered  by 
the  solution. 

The  procedure  for  the  analysis  of  such  a  salt  as  sodium 
chloride  was  as  follows:  the  salt  was  placed  in  the  inner 
compartment  and  diluted  to  about  50  cc.  and  the  anode  placed 
in  position,  while  in  the  outer  compartment,  as  stated  above, 
pure  water  was  placed  and  a  little  sodium  chloride  solution 
so  that  the  current  would  be  conducted  more  rapidly  at  first. 
On  electrolyzing  the  sodium  chloride  in  the  inner  compart- 
ment, the  sodium  passed  into  the  mercury  and  formed  an 
amalgam.  In  a  short  time  this  amalgam  found  its  way  to 
the  outer  compartment,  where  it  was  decomposed  with 
formation  of  sodium  hydroxide.  At  the  conclusion  of  the 
experiment  the  sodium  hydroxide  was  estimated  by  titration 
with  standard  acid,  using  methyl  orange  as  indicator.  The 
chlorine  appeared  as  silver  chloride  at  the  anode  and  was 
perfectly  adherent.  As  nothing  remained  in  the  inner  com- 
partment but  pure  water,  the  needle  of  the  ammeter  gradu- 
ally fell  almost  to  zero.  This  indicated  the  end  of  the  experi- 
ment and  the  anode  was  removed,  dried  and  weighed.  The 
increase  in  weight  represented  the  chlorine  in  the  sodium 
chloride. 


EXPERIMENTAL  PART 

On  experimenting  with  other  anions  than  those  men- 
tioned above,  it  appeared  that  the  silver  anode  was  unsatis- 
factory. In  some  cases,  as  with  a  borate  and  sulphide,  the 
silver  salt  formed  was  not  perfectly  adherent ;  silver  fluoride, 
on  the  other  hand,  was  somewhat  soluble  in  water.  The 
following  experiments  were  instituted,  with  these  facts  in 
mind,  in  the  hope  that  other  anodes  than  silver  might  prove 
helpful. 

LEAD  ANODE 

The  platinum  gauzes  were  plated  with  lead  in  a -bath  of 
lead  sulpho-cyanide  dissolved  in  potassium  hydroxide.  In 
the  experiments  to  be  described  4-5  volts  were  used.  This 
ordinarily  gave  a  current  of  about  0.5  ampere,  falling  to 
0.02-0.01  ampere  when  the  salt  was  completely  removed 
from  the  inner  compartment.  The  anode  was  rotated  250 
times  per  minute.  • 

Potassium  cyanide 

White  lead  cyanide  formed  readily,  but  did  not  adhere 
to  the  anode. 

B  or  ax 
Amperes  0.7-0.03.     The  lead  borate  was  non-adherent. 

Potassium  fluoride 

Amperes  0.7-0.01.  After  many  trials  it  was  again  found 
impossible  to  obtain  a  satisfactory  deposit.  A  considerable 
amount  of  lead  peroxide  formed  on  the  anode.  . 

(7) 


Sodium  sulphate 

Some  lead  sulphate  formed  on  the  anode,  but  the  forma- 
tion of  lead  peroxide  prevented  the  estimation  of  SO4.  By 
titrating  the  caustic  formed  in  the  outer  compartment,  it  was 
possible  to  determine  the  sodium  in  the  salt  with  fair  results. 

Sodium  sulphate  present  0.8520  grams     amperes    volts      time 

"        0.0276       "         o.i-o.oi        5        30  min. 
found    0.0274       " 
0.0274       " 
0.0276       " 

Sodium  sulphide 

The  lead  anode  became  black  as  soon  as  placed  in  the 
solution  of  sodium  sulphide.  However,  as  the  electrolysis 
proceeded,  pieces  of  the  lead  sulphide  became  detached, 
making  an  exact  estimation  of  the  sulphur  impossible.  A 
curious  phenomenon  was  noticed  during  this  experiment. 
The  solution  of  sodium  sulphide  used  was  quite  colorless. 
In  a  few  minutes  the  solution  in  the  inner  compartment  took 
on  a  very  pronounced  yellow  color.  The  same  color  was 
noticed  when  cadmium  and  bismuth  anodes  were  used  with 
soluble  sulphides.  The  cause  of  this  color  wil  shortly  receive 
further  investigation. 

CADMIUM  ANODE 

The  anode  was  plated  in  a  bath  of  potassium  cadmium 
cyanide. 

Sodium  sulphide 

The  formation  of  yellow  cadmium  sulphide  became 
apparent  before  the  current  was  passed.  The  solution  in  the 
inner  compartment  became  yellow,  but  after  a  few  minutes 
became  colorless  again.  The  deposit  of  cadmium  sulphide 
on  the  anode  was  adherent  if  carefullv  handled.  It  was  dried 


in  an  oven  at  115°  and  weighed.  A  low  voltage  should  be 
used  and  care  be  taken  not  to  rotate  the  anode  too  rapidly ; 
otherwise  small  pieces  of  cadmium  sulphide  may  become 
detached. 

Sodium  sulphide  present  0.0429  grams    volts     amperes      time 

"        0.0252       "          3.5       0.1-0.03      15  min. 
found    0.0252      " 
0.0256      " 
0.0251       " 

Sodium  chromate 

The   cadmium  chromate   was   gelatinous   and  non-ad- 
herent. 

Sodium  arsenate 

White  cadmium  arsenate  formed  abundantly,  but  did 
not  adhere  to  the  anode. 


BISMUTH  ANODE 

The  anode  was  plated  from  a  solution  of  bismuth 
nitrate  containing  sulphuric  acid. 

Sodium  chromate 

The  color  of  the  liquid  in  the  inner  compartment  altered 
from  yellow  to  green  and  finally  a  green  gelatinous  precipi- 
tate separated,  probably  chromium  hydroxide.  No  bismuth 
chromate  formed  on  the  anode. 

Sodium  sulphide 

The  liquid  in  the  inner  compartment  again  became 
yellow.  When  a  high  pressure  was  used  (14  volts)  black 
bismuth  sulphide  separated  from  the  liquid.  Little  bismuth 
sulphide  formed  on  the  anode. 


10 

Sodium  ar senate. 

No  bismuth  arsenate  appeared,  indicating  that  the  bis- 
muth was  not  attacked  by  the  arsenate  anion.  The  liquid 
in  the  inner  compartment  became  acid  to  litmus,  probably 
due  to  the  formation  of  arsenic  acid. 

Sodium  iodide 

The  solution  in  the  inner  compartment  assumed  a  deep 
orange  color  at  first.  On  continuing  the  electrolysis  the 
color  became  much  paler.  The  bismuth  anode  did  not 
change  in  appearance. 

ZINC  ANODE 
The  anode  was  plated  from  a  solution  of  sodium  zincate. 

Sodium  phosphate 
White  zinc  phosphate  formed,  but  did  not  adhere. 

Sodium  tungstate 

When  the  anode  was  rotated  slowly,  the  surface  of  the 
mercury  in  the  inner  compartment  took  on  a  blue  iridescent 
tarnish.  No  hydrogen  was  evolved  in  the  outer  compart- 
ment and  the  current  did  not  fall.  Rapid  rotation  of  the 
anode  caused  a  slight  evolution  of  hydrogen  in  the  outer 
compartment  and  a  non-adherent,  white,  flocculent  precipi- 
tate, probably  zinc  tungstate,  formed  in  the  inner  compart- 
ment. In  the  latter  case  the  current  fell  from  o.i-o.oi 
ampere.  Five  volts  were  used  in  each  case. 

•  •    Potassium  cyanate 
A  white,  non-adherent  precipitate  formed. 


II 

Further,  a  copper  anode  was  used  with  a  solution  of 
sodium  arsenite.  The  green  arsenite  of  copper  was  formed 
readily,  but  little  of  it  adhered  to  the  anode.  When  an  iron 
anode  was  used  with  potassium  ferrocyanide,  the  anode  was 
not  attacked  and  hydroferrocyanic  acid  seemed  to  form  in 
the  inner  compartment. 

It  is  clear,  then,  that  the  anodes,  described  above, 
behave  in  several  ways  toward  the  different  anions.  In  some 
cases  an  insoluble  precipitate  is  formed  which  may  or  may 
not  adhere  to  the  anode.  In  other  cases,  for  example,  the 
iron  anode  with  a  soluble  ferrocyanide,  the  anode  is  not 
attacked,  but  the  free  acid  is  generated. 

These  experiments,  while  not  at  all  exhaustive,  seem  to 
indicate  that  silver  is  the  most  suitable  anode  for  receiving 
most  anions.  It  is  entirely  probable  that  further  study  will 
reveal  conditions  under  which  the  other  anodes  will  give 
good  results. 

ELECTROLYSIS  OF  SOLUTIONS  OF  METALLIC  CHLORIDES  WITH 
A  SILVER  ANODE. 

Up  to  this  time  only  salts  of  sodium  and  potassium  had 
been  electrolyzed  in  this  apparatus.  Attention  was  next 
turned  to  other  metals,  using  their  chlorides  with  a  silver 
anode,  to  learn  whether  they  formed  amalgams  and  whether 
the  amalgams,  if  formed,  decomposed  in  the  outer  compart- 
ment with  formation  of  hydroxides.  A  solution  of  calcium 
chloride  was  placed  in  the  inner  compartment  and  electro- 
lyzed in  the  usual  manner.  From  the  appearance  of  the 
surface  of  the  mercury  it  was  evident  that  an  amalgam  was 
formed  at  first,  but  in  a  short  time  it  decomposed  in  the 
inner  compartment,  giving  rise  to  a  large  quantity  of  calcium 
hydroxide.  H.  S.  Lukens,  working  in  this  Laboratory  at 
the  same  time,  found  that  the  amalgams  of  barium  and. 
strontium  deported  themselves  like  those  of  sodium  and 
potassium  and  decomposed  in  the  outer  compartment  with 


12 

formation  of  hydroxides.  He  succeeded  in  making  a  com- 
plete analysis  of  barium  chloride,  weighing  the  chlorine 
collected  at  the  anode  and  titrating  the  barium  hydroxide 
formed  in  the  outer  compartment  in  the  manner  to  be  de- 
scribed later.  These  facts  seemed  so  suggestive  that  solu- 
tions of  a  number  of  the  metallic  chlorides  were  made  up 
and  electrolyzed  with  the  following  results: 

Amalgams  of  lithium,  sodium,  potassium,  calcium  (see 
below),  strontium  and  barium  decompose  in  the  outer  com- 
partment with  formation  of  the  corresponding  hydroxides. 

Amalgams  of  cadmium,  tin,  antimony,  iron,  aluminium, 
chromium,  manganese,  zinc,  nickel,  cobalt,  titanium,  vana- 
dium, zirconium,  thorium,  lanthanum,  cerium,  neodymium, 
praseodymium,  magnesium  and  uranium  decompose  in  the 
inner  compartment  with  formation  of  hydroxides. 


ELECTROLYSIS  OF  CERIUM  CHLORIDE 

A  peculiar  result  was  observed  on  electrolyzing  a  solu- 
tion of  cerous  chloride.  At  the  beginning-  the  appearance  of 
the  surface  of  the  mercury  indicated  the  formation  of  an 
amalgam.  A  subsequent  examination  proved  conclusively 
that  considerable  cerium  had  passed  into  the  mercury.  Later 
the  solution  in  the  inner  compartment  took  on  a  .pink  color, 
which  finally  resembled  a  somewhat  dilute  solution  of  potas- 
sium permanganate.  This  color  was  observed  by  trans- 
mitted light.  It  had  a  greenish,  fluorescent  appearance  by 
reflected  light.  The  solution  was  filtered  without  losing  any 
of  its  properties.  Addition  of  common  salt  produced  a 
brownish  red  precipitate,  which  differed  in  appearance  both 
from  the  hydrated  dioxide  of  cerium,  produced  by  conduct- 
ing chlorine  into  an  alkaline  cerous  salt  and  from  the 
hydrated  trioxide,  produced  by  the  action  of  ammonia  and 


13 

hydrogen  peroxide  on  a  cerous  salt.  The  precipitate  did 
not  dissolve  readily  in  hydrochloric  acid,  but  dissolved  in 
concentrated  sulphuric  acid  with  a  yellow  color.  In  this 
latter  respect  it  resembled  the  dioxide.  The  same  precipitate 
formed  on  allowing  the  purple  solution  to  stand  several 
days  or  on  continuing  the  electrolysis  for  about  an  hour.  A 
pressure  of  8  volts  seemed  to  be  most  favorable  for  the 
formation  of  this  compound.  It  appeared  to  be  a  derivative 
of  cerium  in  a  colloidal  condition.  A  further  study  of  this 
compound  will  be  made  immediately. 


ELECTROLYSIS  OF  CALCIUM  CHLORIDE 

A  more  careful  study  was  next  made  of  the  behavior  of 
calcium  chloride  in  the  cell.  Lukens  found  that  the  salt 
with  which  we  had  been  working  was  contaminated  with 
considerable  amounts  of  magnesium.  The  calcium  was  puri- 
fied by  a  number  of  precipitations  as  oxalate.  On  elec- 
trolyzing  the  pure  chloride,  he  found  that  a  part  of  the 
calcium  appeared  in  the  outer  compartment  like  strontium 
and  barium.  He  was  never  able  to  obtain  all  of  it.  On 
mixing  magnesium  chloride  with  it  again,  none  of  the  cal- 
cium appeared  outside.  With  these  facts  in  mind,  Lukens 
made  a  mixture  of  barium,  calcium  and  magnesium  chlorides 
and  was  able  to  completely  separate  the  barium  from  the 
calcium  and  magnesium.  A  determination  by  the  writer 
gave  the  following  result : 

Barium  chloride  0.1049  grams     volts     amperes       time 
"        present    0.0691      "  3.5      0.5-0.02    2  hours 

found       0.0692       '    (in    presence     of    calcium     and 
magnesium  chlorides) 

All  the  previous  work  had  been  done  with  a  pressure 
of  5  volts  or  under.  It  seemed  probable  to  the  writer  that 
by  using  a  higher  voltage;  all  the  calcium  could  be  removed 


14 

to  the  outer  compartment.     The  following  examples  show 
that  such  is  the  case: 

Calcium  chloride  0.0771    grams  volts     amperes      time 
"        present     0.0278  8        0.1-0.02   2  hours 

"        found        0.0272        " 

0.0280 

0.0278        " 

0.0276        " 

0.0280 

The  estimation  of  the  calcium  was  troublesome  at  first, 
as  the  calcium  hydroxide  which  separated  in  the  outer  com- 
partment was  not  readily  soluble  in  standard  acid  of  con- 
venient strength.  The  difficulty  was  removed  by  adding 
to  the  solution  in  the  outer  part  of  the  cell  a  slight  excess 
of  standard  hydrochloric  acid  at  the  beginning  of  the  experi- 
ment. At  the  conclusion  the  excess  'of  acid  was  estimated 
with  standard  sodium  carbonate  solution,  using  methyl 
orange  as  indicator. 

SEPARATION  OF  CALCIUM  FROM  MAGNESIUM 

By  using  a  still  higher  pressure  it  was  found  possible 
to  separate  calcium  from  magnesium,  although  considerable 
time  was  necessary.  To  remove  the  last  traces  of  calcium 
it  was  found  advantageous  to  add  a  drop  of  hydrochloric 
acid  to  the  solution  in  the  inner  compartment  from  time  to 
time. 

Magnesium  chloride  o.iooo  grams     volts     amperes       time 
Calcium  chloride         0.0771       "  9        0.3-0.02    3  hours 

"        present  0.0278      " 

found  0.0282      " 

0.0276      " 
0.0281      " 

The  calcium  hydroxide  could  be  titrated  directly  in  the 
6uter  compartment  as  described  above,  but  to  obtain  accu- 
rate results  it  was  necessary  to  stir  the  mercury  a  long  time 


15 

with  a  glass  rod  tipped  with  a  piece  of  rubber  to  completely 
decompose  the  amalgam.  It  was  found  more  convenient  to 
remove  the  anode,  siphon  out  the  liquid  in  the  inner  com- 
partment with  .the  magnesium  hydroxide  formed  there,  and 
wash  the  inner  compartment  thoroughly  with  pure  water. 
The  remaining  contents  of  the  cell  were  then  poured  into  a 
large  beaker.  After  stirring  the  mercury  well,  the  titration 
could  be  made  without  difficulty.  This  procedure  was  fol- 
lowed in  all  subsequent  analyses  where  an  insoluble  hy- 
droxide was  formed  in  the  inner  compartment. 

SEPARATION  OF  BARIUM  AND  CALCIUM  FROM  MAGNESIUM 

The  thought  occurred  that  by  mixing  barium,  calcium 
and  magnesium  chlorides,  it  would  be  possible  to  remove 
the  barium  to  the  outer  compartment  with  a  low  pressure, 
estimate  it  and  then  remove  the  calcium  by  increasing  the 
pressure.  Time  did  not  permit  of  the  completion  of  this 
work,  but  a  single  determination  will  show  that  the  separa- 
tion may  be  realized: 

Barium  chloride  0.1049  grams 

Calcium        "  0.0771  " 

Magnesium"  o.iooo  " 

Barium  present  0.0691 

found  0.0691  "       volts  —  3.5 

Calcium  present  0.0278  " 

found  0.0274  "       volts  =  9 

SEPARATIONS 

In  view  of  the  fact  that  the  amalgams  of  the  metals 
divide  themselves  into  two  classes,  some  decomposing  in 
the  outer  and  some  in  the  inner  compartment,  attention  was 
directed  to  separations.  Obviously  there  is  the  possibility  of 
separating  any  metal  in  the  first  class  from  any  metal  in  the 
second  class  and  in  most  of  the  cases  tried  the  separation 
proved  a  success.  The  only  aim  in  this  investigation  was 


i6 

to  discover  whether  the  separations  could  be  made.  No  effort 
was  made  to  reduce  the  time  factor.  The  experiment  was 
usually  begun  at  two  o'clock  and  stopped  between  five  and 
six.  Nor  was  an  effort  made  to  use  larger  quantities  of  the 
metals.  This  would  materially  decrease  the  percentage  error. 
In  order  to  work  with  larger  quantities  it  may  be  found 
advantageous  to  use  anodes  with  a  larger  surface.  These 
points  will  be  worked  out  in  detail  and  the  most  favorable 
conditions  found  for  each  separation. 

SEPARATION  OF  THE  ALKALIES  AND  ALKALINE  EARTHS 
FROM  URANIUM 

These  separations  are  usually  troublesome,  and  it  was 
thought  that  an  electrolytic  separation  might  be  useful. 

SODIUM  FROM  URANIUM 

No  difficulty  was  experienced  in  this  or  the  following 
separation,  although  the  uranium  exercised  a  retarding  influ- 
ence on  the  sodium.  Silver  chloride  formed  on  the  anode 
as  usual  and  the  inner  compartment  became  full  of  yellow 
uranium  hydroxide,  which  later  became  black.  The  sodium 
hydroxide  in  the  outer  compartment  was  titrated  with 
standard  hydrochloric  or  sulphuric  acid. 

Uranium  chloride  o.iooo  grams 

Sodium  chloride      0.1172  volts     amperes       time 

present        0.0461  3-5       0.3-0.02    3  hours 

found  0.0463  " 
0.0459  " 
0-0457 

POTASSIUM  FROM  URANIUM 

Uranium  chloride    o.iooo  grams      volts     amperes      time 
Potassium  chloride  0.1467       "  3-5       0.5-0.01    2  hours 

present    0.0768      " 
found       0.0771       " 
0.0771       " 
0.0766 


I? 

LITHIUM  FROM  URANIUM 

As  lithium  chloride  had  not  been  previously  analyzed 
in  this  cell,  a  solution  was  made  up  and  electrolyzed  with 
the  following  results : 

Lithium  chloride  0.0846  grams     volts     amperes      time  » 

"        present     0.0140       "  5        0.03-0.01    I  hour 

"        found       0.0143 

0.0143 

0.0144 

The  separation  was  made  as  for  sodium  and  potassium 
from  uranium. 

Uranium  chloride  o.iooo  grams     volts     amperes      time 

Lithium  chloride     0.0846  "             5         0.03-0.02    2  hours 
"        present        0.0140 
found           0.0143 

0.0142  " 

0.0141  " 
0.0141 

0.0142  " 

0.0143  " 

BARIUM  FROM  URANIUM 

In  this  separation  the  addition  of  a  few  drops  of  hydro- 
chloric acid  during  the  electrolysis  was  necessary  to  separate 
the  last  traces  of  barium  from  the  uranium.  As  under 
calcium,  a  slight  excess  of  standard  acid  was  added  to  the 
solution  in  the  outer  compartment  at  the  beginning  of  the 
experiment  to  prevent  tfie  formation  of  insoluble  barium 
hydroxide.  The  excess  of  acid  was  estimated  with  standard 
alkali. 

Uranium  chloride    o.iooo  grams     volts     amperes       time 

Barium  chloride        0.1040  "              5       0-15-0.01    I  hour 

"         present         0.0685  " 

"         found            0.0685  " 

0.0688  " 

0.0682  " 
0.0682 


i8 

STRONTIUM  FROM  URANIUM. 
In  this  separation  strontium  bromide  was  used. 

Uranium  chloride    o.iooo  grams     volts     amperes       time 
Strontium  bromide  0.1456      "  5        0.4-0.02   2  hours 

present    0.0513  grams 
found       0.0513       " 
0.0513       " 
0.0516       " 
0.0510       " 


SEPARATION   OF   BARIUM   FROM   THORIUM,   CERIUM,   LAN- 
THANUM AND  NEODYMIUM 

The  following1  separations  were  made  to  further  test 
the  applicability  of  the  method.  As  before,  traces  of  barium 
were  apt  to  remain  with  the  hydroxide  in  the  inner  compart- 
ment unless  a  few  drops  of  hydrochloric  acid  were  added 
during  the  electrolysis. 


BARIUM  FROM  THORIUM 

Thorium  chloride    0.1300  grams     volts     amperes       time 
Barium  chloride       0.1049       "  5        0.4-0.02    2  hours 

"       present         0.0691       " 
found  0.0689       " 

0.0691       " 
0.0689       " 


BARIUM  FROM  CERIUM 

Cerium  chloride    o.iooo  grams     volts     amperes       time 

Barium  chloride    0.1040  "  5        0.4-0.02    2  hours 

"        present      0.0685  " 

"        found        0.0685  " 

0.0684  " 

0.0686  " 


19 
BARIUM  FROM  LANTHANUM 

Lanthanum  chloride   0.0500  grams    volts    amperes      time 
Barium  chloride  0.1049      "  5        0.3-0.01    2  hours 

"      present  0.0691      " 

"      found  0.0693      " 

0.0689      " 

BARIUM  FROM  NEODYMIUM 

Neodymium  chloride  0.1500  grams    volts      amperes      time 
Barium  chloride  0.1049  5         0.5-0.01    2  hours 

"     present  0.0691 

"     found  0.0693      " 

0.0690      " 
0.0693      " 

THALLIUM 

The  similarity  of  thallium  to  the  alkalies  in  many  of  its 
behaviors  raised  the  hope  that  its  amalgam  would  decom- 
pose in  the  outer  compartment  of  the  cell.  Owing  to  the 
insolubility  of  thallous  chloride,  the  sulphate  was  used  in 
connection  with  a  lead  anode.  The  platinum  gauze  was 
plated  with  lead  in  a  very  satisfactory  manner  by  making  it 
the  cathode  in  a  bath  of  hydrofluosilicic  acid.  The  anode 
was  a  strip  of  pure  lead. 

When  thallous  sulphate  was  electrolyzed  in  the  cell,  the 
solution  in  the  outer  compartment  soon  gave  a  very  distinct 
test  for  thallium  with  potassium  iodide.  While  no  quan- 
titative results  can  be  given  as  yet,  it  is  hoped  that  thallium 
can  be  estimated  in  this  way  and  its  separation  from  other 
metals  accomplished. 

AMMONIUM  CHLORIDE 

A  solution  of  ammonium  chloride  was  electrolyzed  with 
a  silver  anode.  An  amalgam  was  formed  in  the  inner  com- 
partment, which  swelled  up  enormously.  It  was  interesting 


20 

to  note  that  the  surface  of  the  mercury  in  the  outer  compart- 
ment became  covered  with  bubbles  and  the  solution  showed 
a  strong  alkaline  reaction,  indicating  that  the  ammonium 
amalgam  had  passed  to  the  outer  compartment  like  the 
amalgams  of  sodium  and  potassium. 

ELECTROLYSIS  OF  A  MIXTURE  OF  SODIUM  AND  POTASSIUM 

CHLORIDES 

The  following  experiments  were  made  to  ascertain 
whether  larger  amounts  of  chlorine  than  formerly  used  could 
be  estimated  with  the  present  form  of  anode.  Hildebrand 
used  a  solution  of  sodium  chloride  containing  0.0708  grams 
of  chlorine.  In  these  determinations  double  the  amount  was 
estimated  with  an  error  of  less  than  0.0005  gram. 

The  method  might  be  used  in  the  estimation  of  a  mix- 
ture of  sodium  and  potassium  as  chlorides.  The  mixed 
chlorides  could  be  weighed,  dissolved  in  water  and  elec- 
trolyzed.  The  chlorine  could  be  weighed  and  the  combined 
sodium  and  potassium  titrated  in  the  outer  compartment. 
The  sodium  and  potassium  could  be  readily  calculated  from 
this  data. 


Sodium  chloride 

0.1166  grams    volts 

amperes      time 

Potassium  chloride  0.1487      "          3-S~5 

0.5-0.02   45  min. 

Chlorine  present 

0.1416 

found 

0.1412      " 

o.  1420      " 

* 

0.1418      " 

0.1420      " 

0.1414      " 

YD  05100 


• 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


